JetBlue Airways stopped all scheduled flights to and from New York and Boston on Monday, and Southwest ground to a halt in Chicago as airlines dealt with a blast of freezing temperatures that caused massive cancellations and delays.

JetBlue resumed some flights in the Northeast on Tuesday morning and is expected to return to full operation at four affected airports by mid-afternoon. It said the time-out would let crews rest and give mechanics a chance to service planes.

With freezing weather stretching from the Midwest to the East Coast, airlines canceled more than 3,700 flights within the U.S. by late afternoon, pushing the three-day total to more than 8,700 U.S. flights wiped out, according to the tracking service FlightAware.com.

JetBlue, which has major operations in Boston and New York, was among the hardest-hit. By late afternoon Monday, it had scrubbed 425 flights, or nearly half its schedule for the day. Some passengers at Boston's Logan Airport had been stuck for two days, sleeping on cots and chairs.

Southwest Airlines Co. suspended flights at Chicago's Midway Airport around midday and canceled more than 100 of its planned 230 daily departures there.

Spokesman Brad Hawkins said that the extreme cold made tasks such as refueling so much longer and more difficult that it the airline couldn't keep its usual schedule.

By late Monday, Southwest had resumed flying at Midway, although Hawkins described the initial activity as "a trickle." The airline's planes are expected to be in position to resume normal operations on Tuesday, he said.

JetBlue spokeswoman Tamara Young said the airline decided to suspend operations at Logan and the three big New York-area airports -- Kennedy, LaGuardia and Newark, N.J. -- because of forecasts that called for temperatures around zero and possible flash freezing.

Young said rules on pilot rest that took effect Saturday contributed to the airline's problems Monday. She said that crews of some delayed planes had to go home because they wouldn't be able to complete their flights within the time allowed by Federal Aviation Administration rules intended to prevent pilots from become overly tired. Young could not put a number on such incidents.

JetBlue hoped to avoid a repeat of the customer-relations disaster that occurred on Valentine's Day 2007, when several of its planes full of passengers were stranded within sight of the Kennedy Airport terminal for up to 10 1/2 hours during a snow storm. That incident led to a federal rule requiring that airlines give passengers a chance to return to the gate within three hours if planes are stuck on the tarmac.

On Monday, JetBlue began shutting down operations in Boston and New York around 1 p.m. EST. The airline said it planned to resume limited service at 10 a.m. Tuesday and full operations by 3 p.m.

JetBlue Airways Corp. shares dropped 39 cents to close at $8.66. The 4.3 percent decline was the steepest among large U.S. airlines in percentage terms. Southwest fell 27 cents, or 1.4 percent, to $19.15.